Fair Value Accounting (Carrying And Estimated Fair Values Of Financial Instruments Carried On Balance Sheet) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financial assets
Trading account assets	$ 26,251
Mortgage loans held for sale	50,439	$ 48,024
Investment securities available for sale	3,990,978	3,987,069
Loans, net	24,625,273	24,538,196
Financial liabilities
Non-interest bearing deposits	7,381,070	7,686,339
Total deposits	26,253,507	26,147,900
Federal funds purchased, other short-term borrowings and other short-term liabilities	185,531	161,190
Long-term debt	1,856,392	1,706,138
Level 1
Financial assets
Cash and cash equivalents	1,059,017	932,933
Trading account assets	0	522
Mortgage loans held for sale	0	0
Other loans held for sale	0	0
Investment securities available for sale	120,931	85,836
Private equity investments	0	0
Mutual funds	3,131
Mutual funds held in rabbi trusts	13,385	14,140
Loans, net	0	0
GGL/SBA loans servicing asset	0	0
Derivative assets	0	0
Financial liabilities
Trading account liabilities	0	0
Non-interest bearing deposits	0	0
Non-time interest bearing deposits	0	0
Time deposits	0	0
Total deposits	0	0
Federal funds purchased, other short-term borrowings and other short-term liabilities	185,531	161,190
Long-term debt	0	0
Earnout liabilities	0	0
Derivative liability positions	0	0
Level 2
Financial assets
Cash and cash equivalents	0	0
Trading account assets	26,251	3,298
Mortgage loans held for sale	50,439	48,024
Other loans held for sale	0	0
Investment securities available for sale	3,868,195	3,899,298
Private equity investments	0	0
Mutual funds	0
Mutual funds held in rabbi trusts	0	0
Loans, net	0	0
GGL/SBA loans servicing asset	0	0
Derivative assets	9,407	11,722
Financial liabilities
Trading account liabilities	23,856	1,000
Non-interest bearing deposits	7,381,070	7,686,339
Non-time interest bearing deposits	14,030,247	13,941,814
Time deposits	4,834,135	4,523,661
Total deposits	26,245,452	26,151,814
Federal funds purchased, other short-term borrowings and other short-term liabilities	0	0
Long-term debt	1,861,008	1,721,814
Earnout liabilities	0	0
Derivative liability positions	16,122	12,767
Level 3
Financial assets
Cash and cash equivalents	0	0
Trading account assets	0	0
Mortgage loans held for sale	0	0
Other loans held for sale	6,591	11,356
Investment securities available for sale	1,852	1,935
Private equity investments	12,715	15,771
Mutual funds	0
Mutual funds held in rabbi trusts	0	0
Loans, net	24,538,259	24,507,141
GGL/SBA loans servicing asset	3,971	4,101
Derivative assets	0	0
Financial liabilities
Trading account liabilities	0	0
Non-interest bearing deposits	0	0
Non-time interest bearing deposits	0	0
Time deposits	0	0
Total deposits	0	0
Federal funds purchased, other short-term borrowings and other short-term liabilities	0	0
Long-term debt	0	0
Earnout liabilities	11,348	11,348
Derivative liability positions	3,974	4,330
Carrying Value
Financial assets
Cash and cash equivalents	1,059,017	932,933
Trading account assets	26,251	3,820
Mortgage loans held for sale	50,439	48,024
Other loans held for sale	6,591	11,356
Investment securities available for sale	3,990,978	3,987,069
Private equity investments	12,715	15,771
Mutual funds	3,131
Mutual funds held in rabbi trusts	13,385	14,140
Loans, net	24,625,273	24,538,196
GGL/SBA loans servicing asset	3,971	4,101
Derivative assets	9,407	11,722
Financial liabilities
Trading account liabilities	23,856	1,000
Non-interest bearing deposits	7,381,070	7,686,339
Non-time interest bearing deposits	14,030,247	13,941,814
Time deposits	4,842,190	4,519,747
Total deposits	26,253,507	26,147,900
Federal funds purchased, other short-term borrowings and other short-term liabilities	185,531	161,190
Long-term debt	1,856,392	1,706,138
Earnout liabilities	11,348	11,348
Derivative liability positions	20,096	17,097
Fair Value
Financial assets
Cash and cash equivalents	1,059,017	932,933
Trading account assets	26,251	3,820
Mortgage loans held for sale	50,439	48,024
Other loans held for sale	6,591	11,356
Investment securities available for sale	3,990,978	3,987,069
Private equity investments	12,715	15,771
Mutual funds	3,131
Mutual funds held in rabbi trusts	13,385	14,140
Loans, net	24,538,259	24,507,141
GGL/SBA loans servicing asset	3,971	4,101
Derivative assets	9,407	11,722
Financial liabilities
Trading account liabilities	0	1,000
Non-interest bearing deposits	7,381,070	7,686,339
Non-time interest bearing deposits	14,030,247	13,941,814
Time deposits	4,834,135	4,523,661
Total deposits	26,245,452	26,151,814
Federal funds purchased, other short-term borrowings and other short-term liabilities	185,531	161,190
Long-term debt	1,861,008	1,721,814
Earnout liabilities	11,348	11,348
Derivative liability positions	$ 20,096	$ 17,097